Methods of automatically regulating operation of ablation members based on determined temperatures

ABSTRACT

Methods and systems for treating tissue that employ a radiometer for temperature measurements and use feedback from the radiometer to regulate energy being applied to the tissue are provided. For example, methods and systems are provided for calculating temperature based on signal(s) from a radiometer, which may provide useful information about tissue temperature at depth, and automatically regulating energy applied to the tissue based on the tissue temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 13/418,136, filed on Mar. 12, 2012, the entirety ofwhich is hereby incorporated by reference herein.

FIELD

This application generally relates to systems and methods for measuringand controlling temperature during tissue ablation.

BACKGROUND

Tissue ablation may be used to treat a variety of clinical disorders.For example, tissue ablation may be used to treat cardiac arrhythmias bydestroying aberrant pathways that would otherwise conduct abnormalelectrical signals to the heart muscle. Several ablation techniques havebeen developed, including cryoablation, microwave ablation, radiofrequency (RF) ablation, and high frequency ultrasound ablation. Forcardiac applications, such techniques are typically performed by aclinician who introduces a catheter having an ablative tip to theendocardium via the venous vasculature, positions the ablative tipadjacent to what the clinician believes to be an appropriate region ofthe endocardium based on tactile feedback, mapping electrocardiogram(ECG) signals, anatomy, and/or fluoroscopic imaging, actuates flow of anirrigant to cool the surface of the selected region, and then actuatesthe ablative tip for a period of time and at a power believed sufficientto destroy tissue in the selected region.

Although commercially available ablative tips may include thermocouplesfor providing temperature feedback via a digital display, suchthermocouples typically do not provide meaningful temperature feedbackduring irrigated ablation. For example, the thermocouple only measuressurface temperature, whereas the heating or cooling of the tissue thatresults in tissue ablation may occur at some depth below the tissuesurface. Moreover, for procedures in which the surface of the tissue iscooled with an irrigant, the thermocouple will measure the temperatureof the irrigant, thus further obscuring any useful information about thetemperature of the tissue, particularly at depth. As such, the clinicianhas no useful feedback regarding the temperature of the tissue as it isbeing ablated or whether the time period of the ablation is sufficient.Because the clinician lacks such information, the clinician furthermorecannot regulate the power of the ablation energy so as to heat or coolthe tissue to the desired temperature for a sufficient period of time.

Accordingly, it may only be revealed after the procedure iscompleted—for example, if the patient continues to experience cardiacarrhythmias—that the targeted aberrant pathway was not adequatelyinterrupted. In such a circumstance, the clinician may not know whetherthe procedure failed because the incorrect region of tissue was ablated,because the ablative tip was not actuated for a sufficient period oftime to destroy the aberrant pathway, because the ablative tip was nottouching or sufficiently touching the tissue, because the power of theablative energy was insufficient, or some combination of the above. Uponrepeating the ablation procedure so as to again attempt to treat thearrhythmia, the clinician may have as little feedback as during thefirst procedure, and thus potentially may again fail to destroy theaberrant pathway. Additionally, there may be some risk that theclinician would re-treat a previously ablated region of the endocardiumand not only ablate the conduction pathway, but damage adjacent tissues.

In some circumstances, to avoid having to repeat the ablation procedureas such, the clinician may ablate a series of regions of the endocardiumalong which the aberrant pathway is believed to lie, so as to improvethe chance of interrupting conduction along that pathway. However, thereis again insufficient feedback to assist the clinician in determiningwhether any of those ablated regions are sufficiently destroyed.

U.S. Pat. No. 4,190,053 to Sterzer describes a hyperthermia treatmentapparatus in which a microwave source is used to deposit energy inliving tissue to effect hyperthermia. The apparatus includes aradiometer for measuring temperature at depth within the tissue, andincludes a controller that feeds back a control signal from theradiometer, corresponding to the measured temperature, to control theapplication of energy from the microwave source. The apparatusalternates between delivering microwave energy from the microwave sourceand measuring the radiant energy with the radiometer to measure thetemperature. As a consequence of this time division multiplexing ofenergy application and temperature measurement, temperature valuesreported by the radiometer are not simultaneous with energy delivery.

U.S. Pat. No. 7,769,469 to Carr et al. describes an integrated heatingand sensing catheter apparatus for treating arrhythmias, tumors and thelike, having a diplexer that permits simultaneous heating andtemperature measurement. This patent too describes that temperaturemeasured by the radiometer may be used to control the application ofenergy, e.g., to maintain a selected heating profile.

Despite the promise of precise temperature measurement sensitivity andcontrol offered by the use of radiometry, there have been few successfulcommercial medical applications of this technology. One drawback ofpreviously-known systems has been an inability to obtain highlyreproducible results due to slight variations in the construction of themicrowave antenna used in the radiometer, which can lead to significantdifferences in measured temperature from one catheter to another.Problems also have arisen with respect to orienting the radiometerantenna on the catheter to adequately capture the radiant energy emittedby the tissue, and with respect to shielding high frequency microwavecomponents in the surgical environment so as to prevent interferencebetween the radiometer components and other devices in the surgicalfield.

Acceptance of microwave-based hyperthermia treatments and temperaturemeasurement techniques also has been impeded by the capital costsassociated with implementing radiometric temperature control schemes.Radiofrequency ablation techniques have developed a substantialfollowing in the medical community, even though such systems can havesevere limitations, such as the inability to accurately measure tissuetemperature at depth, e.g., where irrigation is employed. However, thewidespread acceptance of RF ablation systems, extensive knowledge baseof the medical community with such systems, and the significant costrequired to changeover to, and train for, newer technologies hasdramatically retarded the widespread adoption of radiometry.

In view of the foregoing, it would be desirable to provide apparatus andmethods that permit radiometric measurement of temperature at depth intissue, and permit use of such measurements to control the applicationof ablation energy in an ablation treatment, e.g., a hyperthermia orhypothermia treatment, particularly in an automated fashion so as tomaintain a target region of tissue at a desired temperature for adesired period of time.

It further would be desirable to provide apparatus and methods thatemploy microwave radiometer components that can be readily constructedand calibrated to provide a high degree of measurement reproducibilityand reliability.

It also would be desirable to provide apparatus and methods that permitradiometric temperature measurement and control techniques to beintroduced in a manner that is readily accessible to clinicians trainedin the use of previously-known RF ablation catheters, with a minimum ofretraining.

It still further would be desirable to provide apparatus and methodsthat permit radiometric temperature measurement and control techniquesto be readily employed with previously-known RF electrosurgicalgenerators, thereby reducing the capital costs needed to implement suchnew techniques.

SUMMARY

In view of the foregoing, it would be desirable to provide apparatus andmethods for treating living tissue that employs a radiometer fortemperature measurement, and a temperature control subsystem that usesfeedback from the radiometer to regulate the power of ablation energybeing applied to the tissue. In accordance with one aspect of theinvention, systems and methods are provided for radiometricallymeasuring temperature during RF ablation, i.e., calculating temperaturebased on signal(s) from a radiometer. Unlike standard thermocoupletechniques used in existing commercial ablation systems, a radiometermay provide useful information about tissue temperature at depth—wherethe tissue ablation occurs—and thus provide feedback to the clinicianabout the extent of tissue damage as the clinician ablates a selectedregion of the heart muscle. Furthermore, the temperature controlsubsystem may automatically regulate the power of the ablation energyapplied to the tissue based on the tissue temperature, so as to maintainthe tissue at the desired temperature and for the desired amount of timeto achieve sufficient ablation.

In one embodiment, the present invention comprises an interface module(system) that may be coupled to a previously-known commerciallyavailable ablation energy generator, e.g., an electrosurgical generator,thereby enabling radiometric techniques to be employed with reducedcapital outlay. In this manner, the conventional electrosurgicalgenerator can be used to supply ablative energy to an “integratedcatheter tip” (ICT) that includes an ablative tip, a thermocouple, and aradiometer for detecting the volumetric temperature of tissue subjectedto ablation. The interface module is configured to be coupled betweenthe conventional electrosurgical generator and the ICT, and tocoordinate signals therebetween. The interface module thereby providesthe electrosurgical generator with the information required foroperation, transmits ablative energy to the ICT under the control of theclinician, and displays via a temperature display the temperature atdepth of tissue as it is being ablated, for use by the clinician. Thedisplayed temperature may be calculated based on signal(s) measured bythe radiometer using algorithms such as discussed further below. Theinterface module further includes a temperature control subsystemconfigured to interface with the power control of the electrosurgicalgenerator. The temperature control subsystem stores a setpointtemperature to which the tissue is to be heated, and regulates the powercontrol of the electrosurgical generator based on the setpointtemperature and on the calculated temperature of the tissue so as tobring the calculated tissue temperature to the setpoint temperature andmaintain it at that value for a desired period of time.

In an exemplary embodiment, the interface module includes a firstinput/output (I/O) port that is configured to receive a digitalradiometer signal and a digital thermocouple signal from the ICT, and asecond I/O port that is configured to receive ablative energy from theelectrosurgical generator. The interface module also includes aprocessor, a patient relay in communication with the processor and thefirst and second I/O ports, and a persistent computer-readable medium.The computer-readable medium stores operation parameters for theradiometer and the thermocouple, as well as instructions for theprocessor to use in coordinating operation of the ICT and theelectrosurgical generator.

The computer-readable medium preferably stores instructions that causethe processor to execute the step of calculating a temperature adjacentto the ICT based on the digital radiometer signal, the digitalthermocouple signal, and the operation parameters. This temperature isexpected to provide significantly more accurate information about lesionquality and temperature at depth in the tissue than would a temperaturebased solely on a thermocouple readout. The computer-readable medium mayfurther store instructions for causing the processor to cause thetemperature display to display the calculated temperature, for exampleso that the clinician may control the time period for ablationresponsive to the displayed temperature. The computer-readable mediummay further store instructions for causing the processor to close thepatient relay, such that the patient relay passes ablative energyreceived on the second I/O port, from the electrosurgical generator, tothe first I/O port, to the ICT. Note that the instructions may cause theprocessor to maintain the patient relay in a normally closed state, andto open the patient relay upon detection of unsafe conditions.

The interface module further includes a temperature control subsystemthat regulates the power of the ablative energy based on the calculatedtemperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic illustration of a first embodiment of anarrangement including an interface module, temperature controlsubsystem, and power control interface according to one aspect of thepresent invention, including a display of the front and back panels of,and exemplary connections between, the interface module, temperaturecontrol subsystem, power control interface, a previously known ablationenergy generator, e.g., electrosurgical generator, and an integratedcatheter tip (ICT).

FIG. 1B is a schematic illustrating exemplary connections to and fromthe interface module, temperature control subsystem, and power controlinterface of FIG. 1A, as well as connections among other components thatmay be used with the same.

FIG. 1C is a schematic illustrating exemplary connections to and from analternative embodiment of an interface module, temperature controlsubsystem, and power control interface, as well as connections amongother components that may be used with the same.

FIG. 1D is a schematic illustrating exemplary connections to and fromanother alternative embodiment of an interface module, temperaturecontrol subsystem, and power control interface, as well as connectionsamong other components that may be used with the same.

FIG. 1E is a schematic illustrating exemplary connections to and fromyet another alternative embodiment of an interface module, temperaturecontrol subsystem, and power control interface, as well as connectionsamong other components that may be used with the same.

FIG. 2A is a schematic illustrating internal components of the interfacemodule of FIG. 1A-1B.

FIG. 2B schematically illustrates additional internal components of theinterface module of FIG. 2A, as well as selected connections to and fromthe interface module.

FIG. 2C is a schematic illustrating internal components of thetemperature control subsystem of FIGS. 1A-1B.

FIG. 2D illustrates a perspective view of an exemplary temperaturecontrol subsystem, power control interface, and interface module coupledto each other and to a previously-known ablation energy generator inaccordance with the embodiment illustrated in FIGS. 1A-1B and 2A-2C.

FIG. 3A illustrates steps in a method of using the interface module andtemperature control subsystem of FIGS. 1A-2D during tissue ablation.

FIG. 3B illustrates steps in a method of calculating radiometrictemperature using digital signals from a radiometer and a thermocoupleand operation parameters.

FIG. 3C illustrates steps in a method of controlling an ablationprocedure using a temperature calculated based on signal(s) from aradiometer using the interface module and temperature control subsystemof FIGS. 1A-2D.

FIGS. 4A-4F illustrate data obtained during exemplary ablationprocedures performed using the interface module, temperature controlsubsystem, and power control interface of FIGS. 1A-1B and 2A-2D operatedin accordance with the methods of FIGS. 3A-3C.

FIG. 5A illustrates a plan view of an exemplary patient interface module(PIM) associated with an integrated catheter tip (ICT) for use with theinterface module, temperature control subsystem, and power controlinterface of FIGS. 1A-2D.

FIG. 5B schematically illustrates selected internal components of thePIM of FIG. 5A, according to some embodiments of the present invention.

FIGS. 6A-6B respectively illustrate perspective and exploded views of anexemplary integrated catheter tip (ICT) for use with the interfacemodule, temperature control subsystem, and power control interface ofFIGS. 1A-2D and the PIM of FIGS. 5A-5B, according to some embodiments ofthe present invention.

DETAILED DESCRIPTION

Embodiments of the present invention provide systems and methods forradiometrically measuring temperature during ablation, in particularcardiac ablation, and for automatically regulating the power of ablationenergy based on same. As noted above, commercially available systems forcardiac ablation may include thermocouples for measuring temperature,but such thermocouples may not adequately provide the clinician withinformation about tissue temperature. Thus, the clinician may need tomake an “educated guess” about whether a given region of tissue has beensufficiently ablated to achieve the desired effect. By comparison,calculating a temperature based on signal(s) from a radiometer isexpected to provide accurate information to the clinician about thetemperature of tissue at depth, even during an irrigated procedure.Furthermore, a temperature control subsystem may be employed thatmonitors the calculated temperature, and automatically regulates orcontrols the power of ablation energy provided to the tissue so as tomaintain the tissue at a desired temperature and for a desired time toachieve sufficient ablation. The present invention provides a “retrofit”solution that includes an interface module that works with existing,commercially available ablation energy generators, such aselectrosurgical generators. In accordance with one aspect of the presentinvention, the interface module displays a tissue temperature based onsignal(s) measured by a radiometer and includes, or is connected to, atemperature control subsystem that controls or regulates the power ofablation energy based on same via a power control interface, such that aclinician may perform ablation procedures with significantly betteraccuracy than can be achieved using only a thermocouple for temperaturemeasurement.

First, high level overviews of the interface module, including theconnected or integrated temperature control subsystem and power controlinterface, and connections thereto are provided. Then, further detail onthe internal components of the interface module, temperature controlsubsystem, and power control interface, alternative embodiments thereof,and exemplary methods of calculating radiometric temperature andcontrolling an ablation procedure using the same, are provided. Dataobtained during experimental procedures also is presented. Lastly,further detail on components that may be used with the interface module,temperature control subsystem, and power control interface is provided.

FIG. 1A illustrates plan views of exemplary interface module 110,temperature control subsystem 119, and power control interface, whichare constructed in accordance with the principles of the presentinvention. As described in greater detail below, temperature controlsubsystem 119 is in communication with the power control functionalityof electrosurgical generator 130, and is configured to control the powerof ablation energy generated by generator 130 responsive to thetemperature calculated by interface module 110, by sending appropriatecontrol signals to power control interface 290 that adjusts the powergenerated by generator 130. Temperature control subsystem 119, powercontrol interface 290, and interface module 110 may be separate from oneanother and connected by appropriate cabling as illustrated in FIGS.1A-1B, or alternatively may be integrated into one or more moduleshaving combined functionality, as described in greater detail below withreference to FIGS. 1C-1E.

As illustrated in FIG. 1A, front panel 111 of interface module 110 maybe connected to a catheter 120 that includes patient interface module(PIM) 121 and integrated catheter tip (ICT) 122. Catheter 120 optionallyis steerable, or may be non-steerable and used in conjunction with arobotic positioning system or a third-party steerable sheath (notshown). ICT 122 is positioned by a clinician (optionally with mechanicalassistance such as noted above), during a procedure, within subject 101lying on grounded table 102. ICT 122 may include, among other things, anablative tip, a thermocouple, and a radiometer for detecting thevolumetric temperature of tissue subjected to ablation. The ICT 122optionally includes one or more irrigation ports, which in oneembodiment may be connected directly to a commercially availableirrigant pump.

In embodiments in which the ablation energy is radiofrequency (RF)energy, the ablative tip may include an irrigated ablation electrode,such as described in greater detail below with reference to FIGS. 6A-6B.ICT 122 further may include one or more electrocardiogram (ECG)electrodes for use in monitoring electrical activity of the heart ofsubject 101. Interface module 110 receives signals from thethermocouple, radiometer, and optional ECG electrodes of ICT 122 via PIM121. Interface module 110 provides to ICT 122, via PIM 121, power forthe operation of the PIM and the sensors (thermocouple, radiometer, andECG electrodes), and ablation energy to be applied to subject 101 viathe ablative tip.

Back panel 112 of interface module 110 may be connected via connectioncable 135 to a commercially available previously-known ablation energygenerator 130, for example an electrosurgical generator 130, such as aStockert EP-Shuttle 100 Generator (Stockert GmbH, Freiburg Germany) orStockert 70 RF Generator (Biosense Webster, Diamond Bar, Calif.). Inembodiments where the electrosurgical generator 130 is a StockertEP-Shuttle or 70 RF Generator, generator 130 includes display device 131for displaying temperature and the impedance and time associated withapplication of a dose of RF ablation energy; power control knob 132 forallowing a clinician to manually adjust the power of RF ablative energydelivered to subject 101; and start/stop/mode input 133 for allowing aclinician to initiate or terminate the delivery of RF ablation energy.Start/stop/mode input 133 also may be configured to control the mode ofenergy delivery, e.g., whether the energy is to be cut off after a givenperiod of time.

Although generator 130 may be configured to display temperature ondisplay device 131, that temperature is based on readings from astandard thermocouple. As noted above, however, that reportedtemperature may be inaccurate while irrigant and ablative energy arebeing applied to tissue. Interface module 110 provides to generator 130,via connection cable 135, a thermocouple signal for use in displayingsuch a temperature, and signals from the ECG electrodes; and providesvia indifferent electrode cable 134 a pass-through connection toindifferent electrode 140. Interface module 110 receives from generator130, via connection cable 135, RF ablation energy that module 110controllably provides to ICT 122 for use in ablating tissue of subject101.

As noted above, temperature control subsystem 119 is configured tocontrol the power of ablation energy provided to ICT 122. In theillustrated embodiment, temperature control subsystem 119 is coupled tointerface module 110 via temperature control cable 136, or alternativelymay be an internal component of interface module 110 as described belowwith reference to FIG. 1D. Temperature control subsystem 119 is coupledto power control interface 290 which is operatively coupled to the powercontrol of generator 130, e.g., is mechanically coupled to power controlknob 132, and is configured to regulate ablation power based on thetissue temperature calculated by interface module 110, for example usinga stepper motor 291 as described below with reference to FIG. 2D. In theillustrated embodiment, power control interface 290 is coupled totemperature control subsystem 119 via power control cable 137. However,it should be understood that temperature control subsystem 119 and powercontrol interface 290 may be integrated into a single unit, i.e.,disposed within a single housing, such as described below with referenceto FIG. 1C. Moreover, it should further be understood that temperaturecontrol subsystem 119, power control interface, and interface module 110may be integrated into a single unit, i.e., disposed within a singlehousing, for example as illustrated below with reference to FIG. 1E.

In the embodiment illustrated in FIG. 1A, back panel 112 of interfacemodule 110 includes data ports 114 that are configured to output one ormore signals to temperature control subsystem 119, via control cable136, for use in automatically regulating the power of ablation energygenerated by electrosurgical generator 130. Such signals may include,for example, the tissue temperature calculated by interface module 110,and the power of ablation energy that interface module 110 receives fromgenerator 130. As described in greater detail below, temperature controlsubsystem 119 stores a target temperature (setpoint) to which the tissuetemperature is to be raised, and also includes a processor thatcalculates a power at which the ablation energy is to be provided to ICT122 through interface module 110. The temperature control subsystem 119sends control signals to power control interface 290, via cable 137,that cause the power control interface to mechanically manipulate thepower control knob 132 of generator 130 such that the ablation energy isprovided at this power. Other methods of controlling the power ofablation energy of generator 130 also may be used, for example byinstead transmitting an appropriate control signal to generator 130 tocause generator 130 to output ablation energy at a desired power. Ineither embodiment, the coupling between temperature control subsystem119, power control interface 290, and generator 130 preferably isconfigured such that a clinician may manually override the automatedpower control at any time during an ablation procedure.

As will be familiar to those skilled in the art, for a monopolar RFablation procedure, a clinician may position an indifferent electrode(IE) 140 on the back of subject 101 so as to provide a voltagedifferential that enables transmission of RF energy into the tissue ofthe subject. In the illustrated embodiment, IE 140 is connected tointerface module 110 via first indifferent electrode cable 141.Interface module 110 passes through the IE signal to second indifferentelectrode cable 134, which is connected to an indifferent electrodeinput port on electrosurgical generator 130. Alternatively, the IE maybe connected directly to that port of the electrosurgical generator 130via appropriate cabling (not shown).

It should be understood that electrosurgical generators other than theStockert EP-Shuttle or 70 RF Generator suitably may be used, e.g., othermakes or models of RF electrosurgical generators. Alternatively,generators that produce other types of ablation energy, such asmicrowave generators, cryosurgical sources, or high frequency ultrasoundgenerators, may be used, and the power of ablation energy generated bysuch generators may be suitably regulated using an appropriate mechanism(e.g., by mechanically adjusting a control knob via control interface290 or by providing a control signal via appropriate cabling). Ablationenergy generator 130 need not necessarily be commercially available,although as noted above it may be convenient to use one that is. Itshould also be appreciated that the connections described herein may beprovided on any desired face or panel of interface module 110, and thatthe functionalities of different connectors and input/output (I/O) portsmay be combined or otherwise suitably modified.

Front panel 111 of interface module 110 includes temperature display113, e.g., a digital two or three-digit display device configured todisplay a temperature calculated by a processor internal to interfacemodule 110, e.g., as described in greater detail below with reference toFIGS. 2A-2B and 3A. Other types of temperature displays, such multicolorliquid crystal displays (LCDs), alternatively may be used. Front panel111 also includes connectors (not labeled) through which interfacemodule 110 is connected to ICT 122 via PIM 121, and to the IE 140 viaindifferent electrode cable 141.

Back panel 112 of interface module 110 includes connectors (not labeled)through which interface module 110 is connected to electrosurgicalgenerator 130, via indifferent electrode cable 134 and connection cable135. The data ports 114 of interface module 110, which as noted aboveprovide information to temperature control subsystem 119, also may beconfigured to output one or more signals to a suitably programmedpersonal computer or other remote device, for example an EPmonitoring/recording system such as the LABSYSTEM™ PRO EP RecordingSystem (C.R. Bard, Inc., Lowell, Mass.). Such signals may, for example,include signals generated by the thermocouple, radiometer, and/or ECGelectrodes of the ICT, the tissue temperature calculated by interfacemodule 110, the power of ablation energy being provided to ICT 122, andthe like.

Referring now to FIG. 1B, exemplary connections to and from interfacemodule 110, externally coupled temperature control subsystem 119, andexternally coupled power control interface 290 of FIG. 1A, as well asconnections among other components, are described. Examples ofalternative configurations for partially or fully integratedcombinations of interface module 110, temperature control subsystem 119,and power control interface are described below with reference to FIGS.1C-1E.

In FIG. 1B, interface module 110 is in operable communication withcatheter 120 having an integrated catheter tip (ICT) 122 that includes aradiometer, ablative tip, a thermocouple (TC), and optionally alsoincludes ECG electrodes and/or irrigation ports(s), via patientinterface module (PIM) 121. Interface module 110 is in operablecommunication with temperature control subsystem 119 via temperaturecontrol cable 136, is in operable communication with electrosurgicalgenerator 130 via connection cable 135, and is in operable communicationwith indifferent electrode 140 via indifferent electrode cable 141, suchas discussed above with reference to FIG. 1A. Temperature controlsubsystem 119 is in operable communication with power control interface290 via power control cable 137. Power control interface 290 is inoperable communication with power control 132 of ablation energygenerator 130 via stepper motor 291 described further below withreference to FIG. 2D.

As illustrated in FIG. 1B, electrosurgical generator 130 optionally isin operable communication with electrophysiology (EP)monitoring/recording system 160 via appropriate cabling 161, oralternatively via data ports 114 of interface module 110 and appropriatecabling. EP monitoring/recording system 160 may include, for example,various monitors, processors, and the like that display pertinentinformation about an ablation procedure to a clinician, such as thesubject's heart rate and blood pressure, the temperature recorded by thethermocouple on the catheter tip, the ablation power and time periodover which it is applied, fluoroscopic images, and the like. EPmonitoring/recording systems are commercially available, e.g., theMEDELEC™ Synergy T-EP-EMG/EP Monitoring System (CareFusion, San Diego,Calif.), or the LABSYSTEM™ PRO EP Recording System (C.R. Bard, Inc.,Lowell, Mass.).

If the ICT 122 includes irrigation port(s), then one convenient means ofproviding irrigant to such ports is irrigation pump 140 associated withelectrosurgical generator 130, which pump is in operable communicationwith the generator and in fluidic communication with the ICT viaconnector 151. For example, the Stockert 70 RF Generator is designed foruse with a CoolFlow™ Irrigation pump, also manufactured by BiosenseWebster. Specifically, the Stockert 70 RF Generator and the CoolFlow™pump may be connected to one another by a commercially availableinterface cable, so as to operate as an integrated system that works insubstantially the same way as it would with a standard, commerciallyavailable catheter tip. For example, prior to positioning ICT 122 in thebody, the clinician instructs the pump to provide a low flow rate ofirrigant to the ICT, as it would to a standard catheter tip; the ICT isthen positioned in the body. Then, when the clinician presses the“start” button on the face of generator 130, the generator may instructpump 150 to provide a high flow rate of irrigant for a predeterminedperiod (e.g., 5 seconds) before providing RF ablation energy, again asit would for a standard catheter tip. After the RF ablation energyapplication is terminated, then pump 150 returns to a low flow rateuntil the clinician removes the ICT 122 from the body and manually turnsoff the pump.

As noted above, the functionalities of interface module 110, temperaturecontrol subsystem 119, and/or power control interface 290 optionally maybe integrated with one another. For example, FIG. 1C illustrates anembodiment in which alternative temperature control subsystem 119 c andalternative power control interface 290 c are integrated with oneanother, e.g., located within the same housing with one another.Integrated temperature control subsystem/power control interface 119 c,290 c may be connected to interface module 110 via temperature controlcable 136, and may be connected to power control 132 of ablation energygenerator 130 via stepper motor 291 described further below withreference to FIG. 2D. Other connections may be substantially the same asdescribed above with reference to FIGS. 1A-1B.

Or, for example, FIG. 1D illustrates an embodiment in which interfacemodule 110 d and alternative temperature control subsystem 119 d areintegrated with one another, e.g., located within the same housing withone another. Integrated interface module/temperature control subsystem110 d/119 d may be connected to catheter 120 via PIM 121, may beconnected to ablation energy generator 130 via connection cable 135, andmay be connected to power control 132 of ablation energy generator 130via power control cable 137, power control interface 290, and steppermotor 291. Other connections may be substantially the same as describedabove with reference to FIGS. 1A-1B.

As still another example, FIG. 1E illustrates an embodiment in whichalternative interface module 110 e, alternative temperature controlsubsystem 119 e, and alternative power control interface 290 e areintegrated with one another, e.g., located within the same housing withone another. Integrated interface module/temperature controlsubsystem/power control interface 110 e, 119 e, 290 e may be connectedto ablation energy generator 130 via connection cable 135, and may beconnected to power control 132 of ablation energy generator 130 viastepper motor 291. Other connections may be substantially the same asdescribed above with reference to FIGS. 1A-1B

Referring now to FIGS. 2A-2D, further details of internal components ofinterface module 110, temperature control subsystem 119, and powercontrol interface 290 of FIGS. 1A-1B are provided. It should beunderstood that such components suitably may be modified toalternatively configure module 110, subsystem 119, and interface 290 inpartially or fully integrated modules such as shown in FIGS. 1C-1E.

FIG. 2A schematically illustrates internal components of one embodimentof interface module 110. Interface module 110 includes first, second,third, and fourth ports 201-204 by which it communicates with externalcomponents. Specifically, first port 201 is an input/output (I/O) portconfigured to be connected to catheter 120 via PIM 121, as illustratedin FIG. 1A. Port 201 receives as input from catheter 120 digitalradiometer and digital thermocouple (TC) signals, and optionally ECGsignals, generated by ICT 122, and provides as output to catheter 120 RFablation energy, as well as power for circuitry within the ICT 122 andthe PIM 121. Second port 202 is also an I/O port, configured to beconnected to electrosurgical generator 130 via connection cable 135illustrated in FIG. 1A, and receives as input from generator 130 RFablation energy, and provides as output to generator 130 a reconstitutedanalog thermocouple (TC) signal and raw ECG signal(s). Third port 203 isan input port configured to be connected to indifferent electrode (IE)140 via indifferent electrode cable 134 illustrated in FIG. 1A, andfourth port 204 is an output port configured to be connected togenerator 130 via indifferent electrode cable 141 illustrated in FIG.1A. As shown in FIG. 2A, interface module 110 acts as a pass-through forthe IE signal from IE 140 to generator 130, and simply receives IEsignal on third port 203 and provides the IE signal to generator 130 onfourth port 204.

Interface module 110 also includes processor 210 coupled to non-volatile(persistent) computer-readable memory 230, user interface 280, loadrelay 260, and patient relay 250. Memory 230 stores programming thatcauses processor 210 to perform steps described further below withrespect to FIGS. 3A-3C, thereby controlling the functionality ofinterface module 110. Memory 230 also stores parameters used byprocessor 210. For example, memory 230 may store a set of operationparameters 231 for the thermocouple and radiometer, as well as atemperature calculation module 233, that processor 210 uses to calculatethe radiometric temperature based on the digital TC and radiometersignals received on first I/O port 201, as described in greater detailbelow with respect to FIG. 3B. The operation parameters 231 may beobtained through calibration, or may be fixed. Memory 230 also stores aset of safety parameters 232 that processor 210 uses to maintain safeconditions during an ablation procedure, as described further below withrespect to FIG. 3C. Memory 230 further stores decision module 234 thatprocessor 210 uses to control the opening and closing of patient relay250 and load relay 260 based on its determinations of temperature andsafety conditions, as described further below with reference to FIGS.3A-3C. When closed, patient relay 250 passes ablative energy from thesecond I/O port 202 to the first I/O port 201. When closed, load relay260 returns ablative energy to the IE 140 via dummy load D (resistor,e.g., of 120Ω resistance) and fourth I/O port 204.

As illustrated in FIG. 2A, interface module 110 further includes userinterface 280 by which a user may receive information about thetemperature adjacent ICT 122 as calculated by processor 210, as well asother potentially useful information. In the illustrated embodiment,user interface 280 includes digital temperature display 113, whichdisplays the instantaneous temperature calculated by processor 210. Inother embodiments (not shown), display 113 may be an LCD device that, inaddition to displaying the instantaneous temperature calculated byprocessor 210, also graphically display changes in the temperature overtime for use by the clinician during the ablation procedure. Userinterface 280 further includes data ports 114, one or more of which areconnected to temperature control subsystem 119 to provide the calculatedtemperature and/or ablation energy power to subsystem 119. Data ports114 also optionally may be connected to a computer or EPmonitoring/recording system 160 by appropriate cabling 161 as notedabove, and which may output digital or analog signals being received orgenerated by interface module 110, e.g., radiometer signal(s), athermocouple signal, the ablation energy power, and/or the temperaturecalculated by processor 210.

So as to inhibit potential degradations in the performance of processor210, memory 230, or user interface 280 resulting from electrical contactwith RF energy, interface module 110 may include opto-electronics 299that communicate information to and from processor 210, but thatsubstantially inhibit transmission of RF energy to processor 210, memory230, or user interface 280. This isolation is designated by the dashedline in FIG. 2A. For example, opto-electronics 299 may include circuitrythat is in operable communication with first I/O port 201 so as toreceive the digital TC and radiometer signals from first I/O port 201,and that converts such digital signals into optical digital signals.Opto-electronics 299 also may include an optical transmitter in operablecommunication with such circuitry, that transmits those optical digitalsignals to processor 210 through free space. Opto-electronics 299further may include an optical receiver in operable communication withprocessor 210, that receives such optical digital signals, and circuitrythat converts the optical digital signals into digital signals for useby processor 210. The opto-electronic circuitry in communication withthe processor also may be in operable communication with a secondoptical transmitter, and may receive signals from processor 210 to betransmitted across free space to an optical receiver in communicationwith the circuitry that receives and processes the digital TC andradiometer signals. For example, processor 210 may transmit to suchcircuitry, via an optical signal, a signal that causes the circuitry togenerate an analog version of the TC signal and to provide that analogsignal to the second I/O port. Because opto-electronic circuitry,transmitters, and receivers are known in the art, its specificcomponents are not illustrated in FIG. 2A.

With respect to FIG. 2B, additional internal components of interfacemodule 110 of FIG. 2A are described, as well as selected connections toand from the interface module. FIG. 2B is an exemplary schematic for agrounding and power supply scheme suitable for using interface module110 with an RF electrosurgical generator, e.g., a Stockert EP-Shuttle or70 RF Generator. Other grounding and power supply schemes suitably maybe used with other types, makes, or models of electrosurgicalgenerators, as will be appreciated by those skilled in the art.

As illustrated in FIG. 2B, interface module 110 includes isolated mainpower supply 205 that may be connected to standard three-prong A/C poweroutlet 1, which is grounded to mains ground G. Interface module 110 alsoincludes several internal grounds, designated A, B, C, and I. Internalground A is coupled to the external mains ground G via a relativelysmall capacitance capacitor (e.g., a 10 pF capacitor) and a relativelyhigh resistance resistor (e.g., a 20 MΩ resistor) that substantiallyprevents internal ground A from floating. Internal ground B is coupledto internal ground A via a low resistance pathway (e.g., a pathway orresistor(s) providing less than 1000Ω resistance, e.g., about0Ω/resistance). Similarly, internal ground C is coupled to internalground B via another low resistance pathway. Internal ground I is anisolated ground that is coupled to internal ground C via a relativelysmall capacitance capacitor (e.g., a 10 pF capacitor) and a relativelyhigh resistance resistor (e.g., a 20 MΩ resistor) that substantiallyprevents isolated ground I from floating.

Isolated main power supply 205 is coupled to internal ground A via a lowresistance pathway. Isolated main power supply 205 is also coupled to,and provides power (e.g., ±12V) to, one or more internal isolated powersupplies that in turn provide power to components internal to interfacemodule 110. Such components include, but are not limited to componentsillustrated in FIG. 2A. For example, interface module 110 may includeone or more isolated power supplies 220 that provide power (e.g., ±4V)to processor 210, memory 230, and analog circuitry 240. Analog circuitry240 may include components of user interface 280, including temperaturedisplay 113 and circuitry that appropriately prepares signals for outputon data ports 114. Data ports 114, as well as analog circuitry 240, arecoupled to internal ground B via low resistance pathways, whileprocessor and memory 210, 230 are coupled to internal ground C via lowresistance pathways. Interface module also may include one or moreisolated power supplies 270 that provide power (e.g., ±4V) to ICT 122,PIM 121, and RF circuitry 290.

RF circuitry 290 may include patient and load relays 250, 260, as wellas circuitry that receives the radiometer and thermocouple signals andprovides such signals to the processor via optoelectronic coupling, andcircuitry that generates a clock signal to be provided to the ICT asdescribed further below with reference to FIG. 5B. RF circuitry 290, ICT122, and PIM 121 are coupled to isolated internal ground I via lowresistance pathways.

As shown in FIG. 2B, power supply 139 of RF electrosurgical generator130, which may be external to generator 130 as in FIG. 2B or may beinternal to generator 130, is connected to standard two- or three-prongA/C power outlet 2. However, generator power supply 139 is not connectedto the ground of the outlet, and thus not connected to the mains groundG, as is the isolated main power supply. Instead, generator power supply139 and RF electrosurgical generator 130 are grounded to internalisolated ground I of interface module 110 via low resistance pathwaysbetween generator 130 and PIM 121 and ICT 122, and low resistancepathways between PIM 121 and ICT 122 and internal isolated ground I. Assuch, RF circuitry 290, PIM 121, IE 140, and generator 130 are all“grounded” to an internal isolated ground I that has essentially thesame potential as does ICT 122. Thus, when RF energy is applied to ICT122 from generator 130 through interface module 110, the ground of RFcircuitry 290, PIM 121, ICT 122, IE 140, and generator 130 allessentially float with the RF energy amplitude, which may be a sine waveof 50-100V at 500 kHz.

As further illustrated in FIG. 2B, the ±12V of power that isolated mainpower supply 205 provides to isolated processor/memory/analog powersupply 220 and to isolated ICT/RF power supply 270 may be coupled byparasitic capacitance (pc, approximately 13 pF) to A/C power outlet 1,as may be the ±4V of power that such power supplies provide to theirrespective components. Such parasitic coupling will be familiar to thoseskilled in the art. Note also that the particular resistances,capacitances, and voltages described with reference to FIG. 2B arepurely exemplary and may be suitably varied as appropriate to differentconfigurations.

FIG. 2C schematically illustrates components of temperature controlsubsystem 119, which as noted above may be connected to one or more dataports 114 of interface module 110 via control cable 136 (FIGS. 1A-1B),or alternatively may be included within the housing of interface module110 (FIGS. 1D-1E). In the illustrated embodiment, temperature controlsubsystem 119 includes input port(s) 212, processor 211, memory 235,user input 285, and display 286. Temperature control subsystem 119 isconnected to power control interface 290 via power control cable 137,although power control interface 290 alternatively may be integratedwith temperature control subsystem 119 and/or interface module 110(FIGS. 1C and 1E). Note that the functionalities of processor 210 ofinterface module 110 and processor 211 of temperature control subsystem119 optionally may both be provided by a single processor, particularly(but not necessarily) in embodiments where interface module 110 andtemperature control subsystem 119 are integrated with one another (FIGS.1D-1E). Additionally, or alternatively, the functionalities of memory230 of interface module 110 and memory 235 of temperature controlsubsystem 119 may both be provided by a single memory, particularly (butnot necessarily) in embodiments where interface module 110 andtemperature control subsystem 119 are integrated with one another (FIGS.1D-1E).

As illustrated in FIG. 2C, temperature control subsystem 119 receives oninput port(s) 212, from data port 114, the temperature calculated byprocessor 210 based on signal(s) from the radiometer, as well as thepower of the ablation energy being transmitted to the ICT 122 via firstI/O port 201 of interface module 110. An appropriate ablation energypower meter may be provided within interface module 110 for suchpurpose.

Memory 235 of temperature control subsystem 119, which may be anysuitable persistent, computer-readable medium, stores setpoint 281,ablation time 282, feedback parameters 283, and temperature controlmodule 284. Setpoint 281 is a target temperature at which a region oftissue is to be ablated during an ablation procedure, e.g., 55° C. for acardiac hyperthermia ablation procedure. Ablation time 282 is a targettime for which the region of tissue is to be ablated once the targettemperature is reached, e.g., 60 seconds for a cardiac hyperthermalablation procedure performed at 55° C. Note that appropriate setpointsand times may vary depending on the particular type of ablation beingperformed (e.g., hypothermia, hyperthermia), as well as the location inthe heart where the ablation is being performed. Setpoint 281 and/orablation time 282 may be pre-determined, or alternatively may be inputby a clinician via user input 285. Ablation time 282 alternatively maybe omitted from temperature control subsystem 119, and the ablation timecontrolled via ablation energy generator 130 as described above.Temperature control subsystem 119 may display to the clinician thecalculated temperature, the power of ablation energy, setpoint 281,and/or ablation time 282 via display 286, which may be a single-color ormulti-color digital display such as an LCD or LED.

Feedback parameters 283 define the feedback characteristics of the powerregulation that temperature control subsystem 119 provides. For example,parameters 283 may include a slope with which the power is to be ramped,as well as under-shoot/over-shoot parameters that prevent the power frombeing ramped to too low or too high a power due to delays in thetemperature as the tissue responds to the applied ablation energy.Optionally, one or more of parameters 283 may be adjusted by theclinician via user input 285 and/or displayed to the clinician viadisplay 286. Temperature control module 284 contains a set ofinstructions that cause processor 211 to regulate the power of ablationenergy based on the setpoint 281 and feedback parameters 282 stored inmemory 235 and the calculated temperature and ablation energy powersignals received on input port(s) 212 from data ports 114. Suchinstructions may include steps such as described further below withrespect to FIGS. 3A and 3C.

Temperature control subsystem 119 further is in operable communicationwith power control interface 290 via power control cable 137. Powercontrol interface 290 is configured to be operably coupled to anadjustable power control of electrosurgical generator 130. For example,electrosurgical generator 130 may include an I/O port (not illustrated)through which generator 130 may receive suitable control signals thatdefine a power at which the generator outputs ablation energy, and powercontrol interface 290 may include a control signal generator thatgenerates suitable control signals and passes those control signals tothe generator via an I/O port connected to the port of the generator.

Alternatively, as illustrated in FIG. 1A, electrosurgical generator 130may include a power control knob 132 that, during a conventionalprocedure, a clinician uses to manually adjust the ablation energypower. In some embodiments, the power control interface 290 oftemperature control subsystem 119 may include a suitable mechanism formechanically controlling the ablation energy power via such a powercontrol knob 132. For example, as illustrated in FIG. 2D, power controlinterface 290 may include stepper motor 291, which is coupled to powercontrol knob 132 (not visible in FIG. 2D) of generator 130 viaspring-loaded knob adjuster 292, and which is coupled to temperaturecontrol subsystem 119 via power control cable 137. Stepper motor 291 andspring-loaded knob adjuster 292 may be held in place by bracket 293.Stepper motor 291 includes an on-board mini-controller (not shown) that,responsive to instructions from processor 211 provided via cable 137,rotates knob adjuster 292. Knob adjuster 292 is spring-loaded so as toapply pressure to the face of knob 132, such that rotation of knobadjuster 292 causes knob 132 to rotate and thus to increase or decreasethe ablation energy power by an amount determined by processor 211 basedon the above-noted inputs and parameters. Preferably, knob 132 also maybe manually adjusted even when power control interface 290 is in place,such that a clinician may rapidly intervene and manually adjust theablation energy power as needed during an ablation procedure. Note thatalthough FIG. 2D depicts interface module 110, temperature controlsubsystem 119, and power control interface 290 as being separateelements from one another connected via appropriate cabling, consistentwith FIGS. 1A-1B, such elements alternatively may be partially or fullyintegrated with one another such as described above with reference toFIGS. 1C-1E.

Referring now to FIG. 3A, method 300 of using interface module 110,temperature control subsystem 119, and power control interface 290 ofFIGS. 1A-2D during a tissue ablation procedure is described. Theclinician may couple the integrated catheter tip (ICT) 122 andindifferent electrode (IE) 140 to respective I/O ports of interfacemodule 110 (step 301). For example, as shown in FIG. 1A, ICT 122 may becoupled to a first connector on front panel 111 of interface module 110via patient interface module (PIM) 121, and IE 140 may be coupled to athird connector on front panel 111 via indifferent electrode cable 141.The first connector is in operable communication with first I/O port 201(see FIG. 2A) and the third connector is in operable communication withthird I/O port 203 (see FIG. 2A).

In FIG. 3A, the clinician may couple temperature control subsystem 119to interface module 110 and power control interface 290, and may couplepower control interface 290 to the power control of electrosurgicalgenerator 130 (step 302). For example, as illustrated in FIGS. 1A and2D, temperature control subsystem 119 may be coupled to data port(s) 114of interface module 110 via temperature control cable 136 and may becoupled to power control interface 290 via power control cable 137.Power control interface 290 may be coupled to power control knob 132 ofelectrosurgical generator 130. Note that if interface module 110,temperature control subsystem 119, and/or power control interface 290are partially or fully integrated with one another, then the clinicianneed not separately provide connections between them. Additionally, ifelectrosurgical generator 130 accepts suitable control signals to adjustthe ablation energy power, then the power control interface 290 may becoupled to the generator via appropriate cabling, rather than by amechanical interface such as stepper motor 291.

In FIG. 3A, the clinician may couple electrosurgical generator 130 toI/O port(s) of interface module 110 (step 303). For example, asillustrated in FIG. 1A, electrosurgical generator 130 may be coupled toa second connector on back panel 112 of interface module 110 viaconnection cable 135, and also may be coupled to a fourth connector onback panel 112 via indifferent electrode cable 134. The second connectoris in operable communication with second I/O port 202 (see FIG. 2A), andthe fourth connector is in operable communication with fourth I/O port204 (see FIG. 2A).

In FIG. 3A, the clinician initiates flow of irrigant, positions ICT 122within the subject, e.g., in the subject's heart, and positions IE 140in contact with the subject, e.g., on the subject's back (step 304).Those skilled in the art will be familiar with methods of appropriatelypositioning catheter tips relative to the heart of a subject in anablation procedure, for example via the peripheral arterial or venousvasculature.

Interface module 110 receives digital radiometer, digital thermocouple,and/or analog ECG signals from ICT 122, and receives ablation energyfrom generator 130 (step 305), for example using the connections, ports,and pathways described above with references to FIGS. 1A-2D. Preferably,generator 130 may provide such ablation energy to interface module 110responsive to the clinician pressing “start” using inputs 133 on thefront face of generator 130 (see FIG. 1A).

Interface module 110 calculates and displays the temperature adjacent toICT 122, based on the radiometer and thermocouple signals (step 306).This calculation may be performed, for example, by processor 210 basedon instructions in temperature calculation module 233 stored in memory230 (see FIG. 2A). Exemplary methods of performing such a calculationare described in greater detail below with respect to FIG. 3B.

In method 300, interface module 100 also actuates patient relay 250 soas to provide ablation energy to ICT 122 for use in tissue ablation(step 307). For example, processor 210 maintain patient relay 250illustrated in FIG. 2A in a normally closed state during operation, suchthat ablation energy flows from electrosurgical generator 130 to ICT 122through interface module 110 without delay upon the clinician'sactuation of the generator, and may open patient relay 250 only upondetection of unsafe conditions such as described below with respect toFIG. 3C. In an alternative embodiment, processor 210 may maintainpatient relay 250 in a normally open state during operation, and maydetermine based on instructions in decision module 234 and on thetemperature calculated in step 305 that it is safe to proceed with thetissue ablation, and then close patient relay so as to pass ablationenergy to the ICT. In either case, after a time period defined usinginput 133 on the front face of generator 130, the supply of ablationenergy ceases or the clinician manually turns off the supply of ablationenergy.

Interface module 110 also generates an analog version of thethermocouple signal, and provides the ECG and analog thermocouplesignals to generator 130 (step 308). Preferably, step 308 is performedcontinuously by the interface module throughout steps 304 through 307,rather than just at the end of the ablation procedure. For example, aswill be familiar to those skilled in the art, the Stockert EP-Shuttle or70 RF Generator may “expect” certain signals to function properly, e.g.,those signals that the generator would receive during a standardablation procedure that did not include use of interface module 110. TheStockert EP-Shuttle or 70 RF generator requires as input an analogthermocouple signal, and optionally may accept analog ECG signal(s). Theinterface module 110 thus may pass through the ECG signal(s) generatedby the ICT to the Stockert EP-shuttle or 70 RF generator via second I/Oport 202. However, as described above with reference to FIG. 2A,interface module 110 receives a digital thermocouple signal from ICT122. In its standard configuration, the Stockert EP-Shuttle or 70 RFgenerator is not configured to receive or interpret a digitalthermocouple signal. As such, interface module 110 includes thefunctionality of reconstituting an analog version of the thermocouplesignal, for example using processor 210 and opto-electronics 299, andproviding that analog signal to generator 130 via second I/O port 202.

In FIG. 3A, temperature control module 119 then regulates the power ofablation energy provided to ICT 122 based on the calculated temperatureand on a setpoint, i.e., a target ablation temperature, via powercontrol interface 290 (step 309). For example, as discussed above withrespect to FIGS. 2C-2D, temperature control module 119 receivescalculated temperature and ablation energy power signals from interfacemodule 110, e.g., via data port(s) 114. Based on the received signals,stored setpoint 281, stored ablation time 282, stored feedbackparameters 283, and instructions in temperature control module 284,processor 211 of subsystem 119 determines a power and time at whichablation energy should be provided to the tissue, for example using PI(proportional-integral) or PID (proportional-integral-derivative)control loop feedback algorithms such as known in the art. Then,processor 211 causes power control interface 290 to regulate theablation energy power generated by generator 130 so as to achieve thepower, e.g., by generating an appropriate control signal or bymechanically adjusting the power knob on the face of generator 130.Responsive to the regulation of the ablation energy power, the tissuetemperature may change, resulting in changes to the digital radiometerand/or digital thermocouple signals from the ICT (step 305). The newtemperature may be calculated based on the changed signals (step 306)and the ablation energy power provided to the ICT regulated based on thenew temperature (step 309). As such, the ablation energy power may bedynamically and automatically controlled during the ablation procedureso as to substantially continuously maintain the tissue temperature ator near the setpoint for a desired amount of time, e.g., using PI or PIDcontrol loop feedback algorithms.

Turning to FIG. 3B, the steps of method 350 of calculating radiometrictemperature using digital signals from a radiometer and a thermocoupleand operation parameters is described. The steps of the method may beexecuted by processor 210 based on temperature calculation module 233stored in memory 230 (see FIG. 2A). While some of the signals andoperation parameters discussed below are particular to a PIM and ICTconfigured for use with RF ablation energy, other signals and operationparameters may be suitable for use with a PIM and ICT configured for usewith other types of ablation energy. Those skilled in the art will beable to modify the systems and methods provided herein for use withother types of ablation energy.

In FIG. 3B, processor 210 of interface module 110 obtains from memory230 the operation parameters for the thermocouple (TC) and theradiometer (step 351). These operation parameters may include, forexample, TCSlope, which is the slope of the TC response with respect totemperature; TCOffset, which is the offset of the TC response withrespect to temperature; RadSlope, which is the slope of the radiometerresponse with respect to temperature; TrefSlope, which is the slope of areference temperature signal generated by the radiometer with respect totemperature; and F, which is a scaling factor.

Processor 210 then obtains via first I/O port 201 and opto-electronics299 the raw digital signal from the thermocouple, TCRaw (step 352), andcalculates the thermocouple temperature, TCT, based on TCRaw using thefollowing equation (step 353):

${TCT} = {\frac{TCRaw}{TCSlope} = {TCOffset}}$

Then, processor 210 causes temperature display 113 to display TCT untilboth of the following conditions are satisfied: TCT is in the range of35° C. to 39° C., and ablation energy is being provided to the ICT(e.g., until step 307 of FIG. 3A). There are several reasons to displayonly the thermocouple temperature TCT, as opposed to the temperaturecalculated based on signal(s) from the radiometer, until both of theseconditions are satisfied. For example, if the temperature TCT measuredby the thermocouple is less than 35° C., then based on instructions indecision module 234 the processor 210 interprets that temperature asmeaning that ICT 122 is not positioned within a living human body, whichwould have a temperature of approximately 37° C. If ICT 122 is notpositioned within a living human body, then it would be unsafe toprovide power to the radiometer circuitry, as it may rapidly burn out ifpowered on in air as opposed to blood.

Processor 210 then provides ablation energy to ICT 122, e.g., inaccordance with step 307 described above, and receives via second I/Oport 202 two raw digital signals from the radiometer: Vrad, which is avoltage generated by the radiometer based on the temperature adjacentthe ICT; and Vref, which is a reference voltage generated by theradiometer (step 355). Processor 210 calculates the referencetemperature Tref based on Vrefusing the following equation (step 356):

${Tref} = {\frac{Vref}{TrefSlope} + {TrefOffset}}$

Processor 210 also calculates the radiometric temperature Trad based onVrad and Tref using the following equation (step 357):

${Trad} = {\frac{Vrad}{RadSlope} = {{RadOffset} + {Tref}}}$

During operation of interface module 110, processor 210 may continuouslycalculate TCT, and also may continuously calculate Tref and Trad duringtimes when ablation power is provided to the ICT (which is subject toseveral conditions discussed further herein). Processor 210 may store inmemory 230 these values at specific times and/or continuously, and usethe stored values to perform further temperature calculations. Forexample, processor 210 may store in memory 230 TCT, Tref, and Trad atbaseline, as the respective values TCBase, TrefBase, and TradBase. Theprocessor then re-calculates the current radiometric temperatureTradCurrent based on the current Vrad received on second I/O port 202,but instead with reference to the baseline reference temperatureTrefBase, using the following equation (step 358):

${TradCurrent} = {\frac{Vrad}{RadSlope} - {RadOffset} + {TrefBase}}$

Processor 210 then calculates and causes temperature display 113 todisplay a scaled radiometric temperature TSrad for use by the clinicianbased on the baseline thermocouple temperature TCBase, the baselineradiometer temperature TradBase, and the current radiometer temperatureTradCurrent, using the following equation (step 359):

TSrad=TCBase+(TradCurrent−TradBase)×F

In this manner, interface module 110 displays for the clinician's use atemperature calculated based on signal(s) from the radiometer that isbased not only on voltages generated by the radiometer and its internalreference, described further below with reference to FIGS. 6A-6B, butalso on temperature measured by the thermocouple.

With respect to FIG. 3C, method 360 of controlling an ablation procedurebased on a temperature calculated based on signal(s) from a radiometer,e.g., as calculated using method 350 of FIG. 3B, and also based onsafety parameters 232 and decision module 234 stored in memory 230 ofinterface module 110 (FIG. 2A) and setpoint 281, ablation time 282,feedback parameters 283, and instructions in temperature control module284 stored in memory 235 of temperature control subsystem 119, will nowbe described.

In method 360 of FIG. 3C, a slow flow of irrigant is initiated throughICT 122, and the ICT is then positioned within the subject (step 361).For example, in embodiments using a Stockert 70 RF Generator 130, thegenerator may automatically initiate slow irrigant flow to catheter tip122 by sending appropriate signals to a CoolFlow irrigant pumping system150 associated with the generator, responsive to actuation of thegenerator by the clinician.

The clinician presses a button on generator 130 to start the flow ofablation energy to ICT 122; this may cause the generator to initiate ahigh flow of irrigant to the ICT and generation of ablation energyfollowing a 5 second delay (step 362). Interface module 110 passes theablation energy to ICT 122 via patient relay 250, as described abovewith respect to step 307 of FIG. 3A.

Based on the calculated and displayed temperature (see methods 300 and350 described above with respect to FIGS. 3A-3B), the cliniciandetermines the temperature of the tissue volume that is being ablated bythe ablation energy (step 363). By comparison, temperature measured by athermocouple alone would provide little to no useful information duringthis stage of the procedure.

Then, based on the calculated temperature, the power of ablation energyis automatically regulated so as to achieve the setpoint temperature,e.g., using temperature control subsystem 119 and power controlinterface 290 (step 364). Based on such regulation, the tissuetemperature may change, which change is measured at step 363; the powerof ablation energy may further be regulated based on such changes in thecalculated tissue temperature.

Interface module 110 further may use the calculated radiometrictemperature to determine whether the ablation procedure is beingperformed within safety parameters. For example, processor 210 mayobtain safety parameters 232 from memory 230. Among other things, thesesafety parameters may include a cutoff temperature above which theablation procedure is considered to be “unsafe” because it may result inperforation of the cardiac tissue being ablated, with potentially direconsequences. The cutoff temperature may be any suitable temperaturebelow which one or more unsafe conditions may not occur, for example“popping” such as described below with respect to FIGS. 4E-4F, or tissueburning, but at which the tissue still may be sufficiently heated. Oneexample of a suitable cutoff temperature is 85° C., although higher orlower cutoff temperatures may be used, e.g., 65° C., 70° C., 75° C., 80°C., 90° C., or 95° C. Instructions in decision module 234, also storedin memory 230, cause processor 210 to continuously compare thecalculated radiometric temperature to the cutoff temperature, and if theradiometric temperature exceeds the cutoff temperature, the processormay set an alarm, open the patient relay, and close the load relay so asto return power to the IE via I/O port 204, thereby cutting off flow ofablation energy to the ICT (step 365 of FIG. 3C). Otherwise, theprocessor may allow the ablation procedure to proceed (step 365).

The ablation procedure terminates (step 366), for example, when theclinician presses the appropriate button on generator 130, or when thegenerator 130 automatically cuts of ablation energy at the end of apredetermined period of time.

Referring now to FIGS. 4A-4F, illustrative data obtained during ablationexperiments using interface module 110, optionally with temperaturecontrol subsystem 119, and power control interface 290 constructed andoperated in accordance with the present invention will now be described.This data was obtained using an unmodified Stockert EP Shuttle Generatorwith integrated irrigation pump, and a catheter including the PIM 121and ICT 122 described further below with reference to FIGS. 5A-6B.

FIG. 4A illustrates the change over time in various signals collectedduring an ablation procedure in which ICT 122 was placed against exposedthigh tissue of a living dog, and the Stockert EP Shuttle generatormanually actuated so as to apply 20 W of RF energy for 60 seconds. ALuxtron probe was also inserted at a depth of 3 mm into the dog's thigh.Luxtron probes are considered to provide accurate temperatureinformation, but are impractical for normal use in cardiac ablationprocedures because such probes cannot be placed in the heart of a livingbeing. In this procedure, temperature control subsystem 119 and powercontrol interface 290 were not used, but the data is explained with theintention of orienting the reader as to signals that may be generatedduring an ablation procedure performed using interface module 110; dataobtained during temperature-controlled procedures, in which temperaturecontrol subsystem 119 and power control interface 290 were used withinterface module 110 is provided further below with reference to FIGS.4B-4C.

In FIG. 4A, signal 401 corresponds to scaled radiometric temperatureTSrad; signal 402 corresponds to the thermocouple temperature; signal403 corresponds to a temperature measured by the Luxtron probe; andsignal 404 corresponds to the power generated by the Stockert EP ShuttleGenerator. As can be seen from FIG. 4A, power signal 404 indicates thatRF power was applied to the subject's tissue beginning at a time ofabout 40 seconds and ending at a time of about 100 seconds. Radiometrictemperature signal 401 indicates a sharp rise in temperature beginningat about 40 seconds, from a baseline in region 405 of about 28° C. to amaximum in region 406 of about 67° C., followed by a gradual fall inregion 407 beginning around 100 seconds. The features of radiometrictemperature signal 401 are similar to those of Luxtron probe signal 403,which similarly shows a temperature increase beginning around 40 secondsto a maximum value just before 100 seconds, and then a temperaturedecrease beginning around 100 seconds. This similarity indicates thatthe calculated radiometric temperature 401 has similar accuracy to thatof the Luxtron probe 403. By comparison, thermocouple signal 402 shows asignificantly smaller temperature increase beginning around 40 seconds,followed by a low-level plateau in the 40-100 second region, and then adecrease beginning around 100 seconds. The relatively weak response 402of the thermocouple, and the relatively strong and accurate response ofthe calculated radiometric temperature 401, indicate that an unmodifiedStockert EP Shuttle Generator successfully may be retrofit usinginterface module 110 constructed in accordance with the principles ofthe present invention to provide a clinician with useful radiometrictemperature information for use in an ablation procedure.

FIG. 4B illustrates signals obtained during a similar experimentalprocedure performed in the thigh of a living dog, but in whichtemperature control subsystem 119 and power control interface 290configured illustrated in FIGS. 1A-1B and 2C-2D were coupled tointerface module 110 and used to automatically regulate the ablationpower provided to the animal's tissue to a setpoint (target ablationtemperature) of 80° C. for about 80 seconds. In FIG. 4B, signal 411corresponds to scaled radiometric temperature TSrad; signal 412corresponds to the thermocouple temperature; signal 413 corresponds to atemperature measured by the Luxtron probe; signal 414 corresponds to thepower generated by the Stockert EP Shuttle Generator; signal 415corresponds to the measured tissue impedance; and signal 416 correspondsto Vrad.

In FIG. 4B, beginning around 19 seconds, power signal 414 may be seen toincrease to a maximum of approximately 42 watts as the scaledradiometric temperature signal 411 increases from about 36° C. to about84° C., and the Luxtron probe signal 413 increases from about 29° C. toabout 84° C., while the thermocouple temperature 412 does notsignificantly change. Oscillations 417 may be seen between about 25 and40 seconds in power signal 414 and correspond to rapid adjustments thattemperature control subsystem 119 makes to the ablation power, via powercontrol interface 290, responsive to changes in the scaled radiometrictemperature signal 411. Between about 40-120 seconds, power signal 414then decreases to and stabilizes at about 25 watts, representing thereduced power required to maintain the tissue near the setpointtemperature (rather than to heat the tissue to that temperature, whichrequires additional power). During the same time period, scaledradiometric temperature signal 411 may be seen to stabilize at about 80°C., and Luxtron probe signal 413 to stabilize at around 82° C. At around120 seconds, the ablation power is reduced to zero with concomitantreduction in power signal 414, and thereafter the scaled radiometrictemperature signal 411 and Luxtron probe signal 413 may be seen togradually decrease back to body temperature. Impedance signal 415 may beseen to increase and then stabilize during application of ablation powerbetween about 19-120 seconds, while Vrad signal 416 may be seen todecrease during this time period.

FIG. 4C illustrates signals obtained during a similar experimentalprocedure performed in the beating of a living dog, and in whichtemperature control subsystem 119 and power control interface 290configured illustrated in FIGS. 1A-1B and 2C-2D were coupled tointerface module 110 and used to automatically regulate the ablationpower provided to the animal's tissue to a setpoint (target ablationtemperature) of 80° C. for about 60 seconds. In FIG. 4C, signal 421corresponds to scaled radiometric temperature TSrad; signal 422corresponds to the thermocouple temperature; signal 424 corresponds tothe power generated by the Stockert EP Shuttle Generator; signal 425corresponds to the measured tissue impedance; and signal 426 correspondsto Vrad. A Luxtron probe was not used during this procedure because itwas performed in a beating heart.

In FIG. 4C, beginning around 18 seconds, power signal 424 may be seen toincrease to a maximum of approximately 30 watts as the scaledradiometric temperature signal 421 increases from about 40° C. to about85° C., while the thermocouple temperature 422 does not significantlychange. Oscillations 427 may be seen between about 25 and 45 seconds inpower signal 424 and correspond to rapid adjustments that temperaturecontrol subsystem 119 makes to the ablation power, via power controlinterface 290, responsive to changes in the scaled radiometrictemperature signal 421. Between about 45-78 seconds, power signal 424then decreases to and stabilizes at about 17 watts, representing thereduced power required to maintain the tissue near the setpointtemperature (rather than to heat the tissue to that temperature, whichrequires additional power). During this same time period, scaledradiometric temperature signal 421 may be seen to stabilize at about 80°C. At around 78 seconds, the ablation power is reduced to zero withconcomitant reduction in power signal 424, and thereafter the scaledradiometric temperature signal 421 may be seen to gradually decreaseback to body temperature. Impedance signal 425 may be seen to increaseand then stabilize during application of ablation power between about18-78 seconds, while oscillating as a result of the beating of theheart, while Vrad signal 426 may be seen to decrease and oscillateduring this time period.

Additional experimental data obtained during other procedures in whichtemperature control subsystem 119 and power control interface 290 werenot used will now be described with reference to FIGS. 4D-4F, so as tomore fully explain the functionality of interface module 110. It will beappreciated that coupling interface module 110 to temperature controlsubsystem 119 and power control interface 290 may provide additionalenhanced functionalities, including temperature control, such asdescribed further above.

FIG. 4D illustrates signals obtained during an experimental proceduresimilar to that described above with reference to FIG. 4A, and in whichtwo Luxtron probes were implanted into the thigh tissue of a living dog,the first at a depth of 3 mm and the second at a depth of 7 mm. TheStockert EP Shuttle generator was activated, and the RF power wasmanually modulated between 5 and 50 W using power control knob 132 onthe front panel of the generator. In FIG. 4D, the scaled radiometrictemperature signal is designated 431, the 3 mm Luxtron signal designated432, and the 7 mm Luxtron designated 433. The scaled radiometrictemperature signal 431 and the 3 mm Luxtron signal 432 may be seen tohave relatively similar changes in amplitude to one another resultingfrom the periodic heating of the tissue by RF energy. The 7 mm Luxtronsignal 433 may be seen to have a slight periodicity, but far lessmodulation than do the radiometric temperature and 3 mm Luxtron signals431, 432. This is because the 7 mm Luxtron is sufficiently deep withinthe tissue that ablation energy substantially does not directlypenetrate at that depth. Instead, the tissue at 7 mm may be seen toslowly warm as a function of time, as heat deposited in shallowerportions of the tissue gradually diffuses to a depth of 7 mm.

FIGS. 4A-4F illustrate data obtained during a series of cardiac ablationprocedures that were also performed in living humans using theexperimental setup described above with respect to FIG. 4C, but omittingtemperature control subsystem 119 and power control interface 290. Thehumans all suffered from atrial flutter, were scheduled for conventionalcardiac ablation procedures for the treatment of same, and consented tothe clinician's use of the interface box and ICT during the procedures.The procedures were performed by a clinician who introduced the ICT intothe individuals' endocardia using conventional methods. During theprocedures, the clinician was not allowed to view the temperaturecalculated by the interface module. As such, the clinician performed theprocedures in the same manner as they would have done with a systemincluding a conventional RF ablation catheter directly connected to aStockert EP-Shuttle generator. The temperature calculated by theinterface module during the various procedures was made available forthe clinician to review at a later time. The clinician performed a totalof 113 ablation procedures on five humans using the above-notedexperimental setup.

FIG. 4E illustrates the change over time in signal 441 corresponding tothe scaled radiometric temperature TSrad, as well as the change overtime in the signal 442 corresponding to the thermocouple temperature,during the tenth ablation procedure performed on the individual. Duringthe procedure, about 40 W of RF power was applied to the individual'scardiac tissue for 60 seconds (between about 20 seconds and 80 secondsin FIG. 4E), and the clinician had a target temperature 445 of 55° C. towhich it was desired to heat the cardiac tissue so as to sufficientlyinterrupt an aberrant pathway causing the individual's atrial flutter.It can be seen that the scaled radiometric temperature signal 441, whichwas subjected to data smoothing in FIG. 4E, varied between about 40° C.and 51° C. while RF power was applied and manually controlled by theclinician via control knob 132. By comparison, as expected, thethermocouple temperature 442 provided essentially no useful informationabout the tissue temperature during the procedure. Notably, theclinician's target temperature 445 of 55° C. was never reached duringthe procedure, even though the clinician believed based on his or herperceptions of the procedure that such temperature had been reached bymanually adjusting the RF power via control knob 132. Because the targettemperature 445 was not reached, the tissue was insufficiently heatedduring the procedure to interrupt an aberrant pathway. The failure toreach the target temperature may be attributed to insufficient contactand/or force between the ablative tip of the ICT and the individual'scardiac tissue, the condition of the cardiac surface, insufficientpower, and the like.

FIG. 4F illustrates the change over time in signal 451 corresponding toTSrad, as well as the change over time in signal 452 corresponding tothe thermocouple temperature, during the eleventh ablation procedureperformed on the same individual as in FIG. 4E. During this procedure,again about 40 W of RF power was applied to the individual's cardiactissue for 60 seconds (between about 20 seconds and 80 seconds in FIG.4E), and the clinician again had a target temperature 455 of 55° C. Itcan be seen that the scaled radiometric signal 451, again subject todata smoothing, varied between about 55° C. and 70° C. while RF powerwas applied and manually controlled by the clinician via control knob132, while the thermocouple temperature 452 again provided essentiallyno useful information. Here, the clinician attributed the highertemperature tissue temperature achieved during the ablation to bettercontact between the ablative tip of the ICT and the individual's cardiactissue. However, it can be seen that even while RF power was beingapplied to the tissue, the temperature varied relatively rapidly overtime, e.g., from about 70° C. at about 35 seconds, to about 56° C. at 40seconds, which may be attributed to variations in the quality of contactbetween the ICT and the individual's cardiac tissue.

The results of the ablation procedures performed on the five individualsare summarized in the following table:

% of Total Total Ablation Number of patients 5 Number of ablations 113Number of ablations that did not reach target 50 44% temperature of 55°C. Number of ablations that reach high temperature 13 12% cutoff of 95°C. Number of pops 3 3% Number of successful treatments of atrial flutter5 100%

As can be seen from the above table, 44% of the ablation procedures didnot reach the clinician's target tissue temperature of 55° C. As such,it is likely that this percentage of the procedures resulted ininsufficient tissue heating to interrupt aberrant pathway(s). However,although many of the ablation procedures failed, the clinician repeatedthe ablation procedures a sufficient number of times to achieve 100%treatment of the individuals' atrial flutter. It is believed thatdisplaying the calculated temperature to the clinician during ablationprocedures would enable the clinician to far more accurately assess thequality of contact between the ablative tip of the ICT and theindividual's cardiac tissue, and thus to sufficiently heat the tissueabove the target temperature for a desired period of time, and thusreduce the clinicians' need to repeatedly perform numerous ablationprocedures on the same subject so as to achieve the desired treatment.Moreover, it is believed that automatically controlling the ablationpower during ablation procedures would provide the clinician withgreater control over lesion formation, thus improving the percentage ofeffective lesions and reducing the incidence of pops and burns.

As shown in the above table, 12% of the ablation procedures triggeredthe high temperature cutoff such as illustrated in FIG. 3C. Here, thecutoff temperature was defined to be 95 C. However, it was observed thatat this cutoff temperature, “pops” formed during three of the ablationprocedures. A “pop” occurs when the blood boils because of excessivelocalized heating caused by ablation energy, which results in formationof a rapidly expanding bubble of hot gas that may cause catastrophicdamage to the cardiac tissue. It is believed that a lower cutofftemperature, e.g., 85° C., may inhibit formation of such “pops.”

Additional components that may be used in conjunction with interfacemodule 110, temperature control subsystem 119, and power controlinterface 290 of the present invention, e.g., a PIM 121 and ICT 122 ofcatheter 120, are now briefly described with reference to FIGS. 5A-6B.

In FIG. 5A, patient interface module (PIM) 121 that may be associatedwith the integrated catheter tip (ICT) described further below withrespect to FIGS. 6A-6B is described. PIM 121 includes interface moduleconnector 501 that may be connected to front panel 111 of interfacemodule 110, as described with reference to FIG. 1A; PIM circuitry 502,which will be described in greater detail below with reference to FIG.5B; ICT connector 503 that may be connected to catheter 120; and PIMcable 504 that extends between interface module connector 501 and PIMcircuitry 502. PIM 121 is preferably, but not necessarily, designed toremain outside the sterile field during the ablation procedure, andoptionally is reusable with multiple ICT's.

FIG. 5B schematically illustrates internal components of PIM circuitry502, and includes first I/O port 505 configured to be coupled tocatheter 120, e.g., via ICT connector 503, and second I/O port 506configured to be coupled to interface module 110, e.g., via PIM cable504 and interface module connector 501.

PIM circuitry 502 receives on first I/O port 505 an analog thermocouple(TC) signal, raw analog radiometer signals, and analog ECG signals fromcatheter 120. PIM circuitry 502 includes TC signal analog-to-digital(A/D) converter 540 that is configured to convert the analog TC signalto a digital TC signal, and provide the digital TC signal to interfacemodule 110 via second I/O port 506. PIM circuitry 502 includes a seriesof components configured to convert the raw analog radiometer signalsinto a usable digital form. For example, PIM circuitry may includeradiometric signal filter 510 configured to filter residual RF energyfrom the raw analog radiometer signals; radiometric signal decoder 520configured to decode the filtered signals into analog versions of theVref and Vrad signals mentioned above with reference to FIG. 3B; andradiometric signal A/D converter 530 configured to convert the analogVref, Vrad signals into digital Vref, Vrad signals and to provide thosedigital signals to second I/O port for transmission to interface module110. PIM circuitry 502 also passes through the ECG signals to second I/Oport 506 for transmission to interface module 110.

On second I/O port 506, PIM circuitry 502 receives RF ablation energyfrom generator 130 (e.g., a Stockert EP-Shuttle or 70 RF Generator) viainterface module 110. PIM circuitry 502 passes that RF ablation energythrough to catheter 120 via first I/O port 505. PIM circuitry 502 alsoreceives on second I/O port 506 a clock signal generated by RF circuitrywithin interface module 110, as described further above with referenceto FIG. 2B, and passes through the clock signal to first I/O port 505for use in controlling microwave circuitry in ICT 122, as describedbelow.

Referring now to FIGS. 6A-6B, an exemplary integrated catheter tip (ICT)122 for use with the interface module 110, temperature control subsystem119, and power control interface 290 of FIGS. 1A-2D and the PIM of FIGS.5A-5B is described. Further detail on components of ICT 122 may be foundin U.S. Pat. No. 7,769,469 to Carr, the entire contents of which areincorporated herein by reference, as well as in U.S. Patent PublicationNo. 2010/0076424, also to Can (“the Can publication”), the entirecontents of which are incorporated herein by reference. The devicedescribed in the aforementioned patent and publication do not include athermocouple or ECG electrodes, which preferably are included in ICT 122configured for use with interface module 110.

As described in the Can publication and as depicted in FIGS. 6A-6B, ICT122 includes an inner or center conductor 103 supported by a conductivecarrier or insert 104. Carrier 104 may be formed from a cylindricalmetal body having an axial passage 106 that receives conductor 103.Upper and lower sectors of that body extending inward from the ends maybe milled away to expose passage 106 and conductor 103 therein and toform upper and lower substantially parallel flats 108 a and 108 b. Flat108 a may include coplanar rectangular areas 108 aa spaced on oppositesides of conductor 103 near the top thereof. Likewise, flat 108 b mayinclude two coplanar rectangular areas 108 bb spaced on opposite sidesof conductor 103 near the bottom thereof. Thus, carrier 104 may includecenter segment 104 a containing the flats and distal and proximal endsegments 104 b and 104 c, respectively, which remain cylindrical, exceptthat a vertical groove 107 may be formed in proximal segment 104 c.

Center conductor 103 may be fixed coaxially within passage 106 by meansof an electrically insulating collar or bushing 109, e.g. of PTFE, pressfit into passage 106 at distal end segment 104 b of the carrier and by aweld to the passage wall or by an electrically conductive collar orbushing (not shown) at the carrier proximal segment 104 c. This causes ashort circuit between conductor 103 and carrier 104 at the proximal endof the carrier, while an open circuit may be present therebetween at thedistal end of the carrier. In the carrier center segment 104 a, thewalls 106 a of passage 106 may be spaced from center conductor 103. Thisforms a quarter wave stub S, as described in greater detail in U.S. Pat.No. 7,769,469 and U.S. Patent Publication No. 2010/0076424. Conductor103 includes distal end segment 103 a which extends beyond the distalend of carrier 104 a selected distance, and a proximal end segment 103 bwhich extends from the proximal end of ICT 122 and connects to thecenter conductor of cable 105 configured to connect to PIM 121.

As illustrated in FIG. 6B, mounted to the upper and lower flats 108 aand 108 b of carrier 104 is a pair of opposed, parallel, mirror-image,generally rectangular plates 115 a and 115 b. Each plate 115 a, 115 bmay include a thin, e.g. 0.005 in., substrate 116 formed of anelectrically insulating material having a high dielectric constant.Printed, plated or otherwise formed on the opposing or facing surfacesof substrates 116 are axially centered, lengthwise conductive strips117, preferably 0.013-0.016 mm wide, which extend the entire lengths ofsubstrates 116. Also, the opposite or away-facing surfaces of substrates116 are plated with conductive layers 118, e.g. of gold. The side edgesof layers 118 wrap around the side edges of the substrates.

When the ICT is being assembled, plate 115 a may be seated on the upperflat 108 a of carrier 104 and the lower plate 115 b is likewise seatedon the lower flat 108 b so that the center conductor 103 is contactedfrom above and below by the conductive strips 117 of the upper and lowerplates and the layer 118 side edges of those plates contact carriersegment 104 a. A suitable conductive epoxy or cement may be appliedbetween those contacting surfaces to secure the plates in place.

At least one of the plates, e.g. plate 115 a, functions also as asupport surface for one or more monolithic integrated circuit chips(MMICs), e.g. chips 122 and 124. The chip(s) may include a couplingcapacitor connected by a lead (not shown) to center conductor 103 andthe usual components of a radiometer such as a Dicke switch, a noisesource to provide a reference temperature, amplifier stages, a band passfilter to establish the radiometer bandwidth, additional gain stages ifneeded, a detector and buffer amplifier. Due to the relatively smallprofile of the present ICT 122, the above circuit components may bearranged in a string of four chips. The chip(s) may be secured to themetal layer 118 of plate 115 a by a suitable conductive adhesive so thatthat layer which, as described above, is grounded to the insert 104 mayfunction as a ground plane for those chips. The plates also conduct heataway from the chips to conductor 103 and carrier 104. Various leads (notshown) connect the chips to each other and other leads 125 b extendthrough carrier slot 107 and connect the last chip 124 in the string,i.e. the radiometer output, to corresponding conductors of cable 105leading to PIM 121.

A tubular outer conductor 126 may be slid onto carrier 104 from an endthereof so that it snugly engages around the carrier with its proximaland distal ends coinciding with the corresponding ends of the carrier(not shown). The conductor 126 may be fixed in place by a conductiveepoxy or cement applied around the carrier segments 104 b and 104 c.

ICT 122 also may include an annular dielectric spacer 137, e.g. of PTFE,which is centered on the distal end of carrier 104 and surrounds theconductor segment 103 a. The spacer may have a slit 137 a enabling it tobe engaged around that conductor segment from the side thereof. Thespacer 137 may be held in place by a conductive collar 136 whichencircles the spacer and is long enough to slidably engage over a distalend segment of outer conductor 126. The collar 136 may be press fitaround that conductor and carrier segment 104 b to hold it in place andto electrically connect all those elements.

The distal end of the ICT 122 may be closed off by conductive tip 142which, in axial section, may be T shaped. That is, the tip 142 may havediscoid head 142 a that forms the distal end of the ICT and an axiallyextending tubular neck 142 b. The conductor segment 103 a issufficiently long to extend beyond the distal end of the spacer 137 intothe axial passage in neck 104 b. The tip may be secured in place byconductive adhesive applied around the distal end of conductor segment103 a and at the distal end or edge of collar 136. When the tip is inplace, the conductor segment 103 a and tip 104 form a radiometricreceiving antenna, as described in greater detail in U.S. Pat. No.7,769,469 and U.S. Patent Publication No. 2010/0076424.

ICT 122 may further include dielectric sheath 144 which may be engagedover the rear end of outer conductor 126 and slid forwardly until itsdistal end 144 a is spaced a selected distance behind the distal end oftip 142. The conductors 103 and 126 of ICT 122 form an RF transmissionline terminated by the tip 104. When the ICT 122 is operative, thetransmission line may radiate energy for heating tissue only from theuninsulated segment of the probe between tip 104 and the distal end 144a of the sheath 144. That segment thus constitutes an RF ablationantenna.

The proximal ends of the center conductor segment 103 b, outer conductor126 and sheath 144 may be connected, respectively, to the inner andouter conductors and outer sheath of cable 105 that leads to PIM 121.Alternatively, those elements may be extensions of the correspondingcomponents of cable 105. In any event, that cable 105 connects thecenter conductor 103 to the output of a transmitter which transmits a RFheating signal at a selected heating frequency, e.g. 500 GHz, to the RFablation antenna.

As illustrated in FIG. 6A, ICT 122 further may include first, second,and third ECG electrodes 190 disposed on the outside of sheath 144, aswell as a thermocouple 191 positioned so as to detect the temperature ofblood or tissue in contact with ICT 122. Signals generated by electrodes190 and thermocouple 191 may be provided along cable 105 connected toPIM 121.

If desired, cable 105 further may include probe steering wire 145 whoseleading end 145 a may be secured to the wall of a passage 146 in carriersegment 104 c.

Preferably, helical through slot 147 is provided in collar 136 as shownin FIGS. 6A-6B. The collar material left between the slot turnsessentially forms helical wire 148 that bridges spacer 137. Wire 148 isfound to improve the microwave antenna pattern of the radiometricreceiving antenna without materially degrading the RF heating pattern ofthe RF ablation antenna.

The inner or center conductor 103 may be a solid wire, or preferably isformed as a tube that enables conductor 103 to carry an irrigation fluidor coolant to the interior of probe tip 142 for distribution therefromthrough radial passages 155 in tip head 142 a that communicate with thedistal end of the axial passage in tip neck 142 b.

When plates 115 a and 115 b are seated on and secured to the upper andlower flats 108 a and 108 b, respectively, of carrier 104, conductivestrips 117, 117 of those members may be electrically connected to centerconductor 103 at the top and bottom thereof so that conductor 103 formsthe center conducts for of a slab-type transmission line whose groundplane includes layers 118, 118.

When ablation energy is provided to ICT 122, a microwave field existswithin the substrate 116 and is concentrated between the centerconductor 103 and layers 118, 118. Preferably, as noted here, conductiveepoxy is applied between conductor 103 and strips 117 to ensure that noair gaps exist there because such a gap would have a significant effecton the impedance of the transmission line as the highest field parts areclosest to conductor 103.

Plates 115 a, 115 b and conductor 103 segment together with carrier 104form a quarter wave (λ_(R)/4) stub S that may be tuned to the frequencyof radiometer circuit 124, e.g. 4 GHz. The quarter wave stub S may betuned to the center frequency of the radiometer circuit along withcomponents in chips 122, 124 to form a low pass filter in the signaltransmitting path to the RF ablation antenna, while other components ofthe chips form a high pass or band pass filter in the signal receivingpath from the antenna to the radiometer. The combination forms a passivediplexer D which prevents the lower frequency transmitter signals on thesignal transmitting path from antenna T from reaching the radiometer,while isolating the path to the transmitter from the higher frequencysignals on the signal receiving path from the antenna.

The impedance of the quarter wave stub S depends upon the K value andthickness t of substrates 116 of the two plates 115 a, 115 b and thespacing of center conductor 103 from the walls 106 a, 106 a of passage106 in the carrier center segment 104 a. Because the center conductor103 is not surrounded by a ceramic sleeve, those walls can be movedcloser to the center conductor, enabling accurate tuning of thesuspended substrate transmission line impedance while minimizing theoverall diameter of the ICT 122. As noted above, the length of the stubS may also be reduced by making substrate 116 of a dielectric materialwhich has a relatively high K value.

In one working embodiment of the ICT 122, which is only about 0.43 in.long and about 0.08 in. in diameter, the components of the ICT have thefollowing dimensions:

Component Dimension (inches) Conductor 103 0.020 outer diameter 0.016inner diameter (if hollow) Substrate 116 (K = 9.8) 0.065 wide; thicknesst = 0.005 Strips 117 0.015 wide Air gap between 103 and each 106a 0.015

Thus, the overall length and diameter of the ICT 122 may be relativelysmall, which is a useful feature for devices configured for percutaneoususe.

While various illustrative embodiments of the invention are describedabove, it will be apparent to one skilled in the art that variouschanges and modifications may be made herein without departing from theinvention. For example, although the interface module has primarily beendescribed with reference for use with an RF electrosurgical generatorand the PIM and ICT illustrated in FIGS. 5A-6B, it should be understoodthat the interface module suitably may be adapted for use with othersources of ablation energy and other types of radiometers. Moreover, theradiometer may have components in the ICT and/or the PIM, and need notnecessarily be located entirely in the ICT. Furthermore, thefunctionality of the radiometer, ICT, and/or PIM optionally maybeincluded in the interface module. The appended claims are intended tocover all such changes and modifications that fall within the truespirit and scope of the invention.

1. (canceled)
 2. A method of determining a temperature and facilitatingablation of tissue of a subject, comprising: positioning a catheter ofan ablation system at a target anatomical location of a subject; whereinan integrated catheter tip is positioned along a distal end of thecatheter, the integrated catheter tip comprising a radiofrequencyelectrode, a radiometer and a temperature-measurement device, whereinthe ablation system further comprises a generator for providing energyto the radiofrequency electrode; and wherein the ablation system furthercomprises a non-transitory computer-readable medium and a processor;determining a temperature of a tissue of the subject at a depth relativeto a surface of the tissue based on, at least in part, a signalgenerated by the radiometer, a signal generated by thetemperature-measurement device and operation parameters for theradiometer and the temperature-measurement device stored on thecomputer-readable medium; delivering radiofrequency energy to the tissueof the subject by activating the generator to provide power to theradiofrequency electrode; and automatically regulating operation of theradiofrequency electrode based, at least in part, on the determinedtemperature.
 3. The method of claim 2, wherein automatically regulatingthe operation of the radiofrequency electrode comprises regulating theoperation of the radiofrequency electrode to maintain the determinedtemperature of the tissue within a target temperature setpoint or range.4. The method of claim 2, further comprising delivering irrigation fluidto a fluid passage of the catheter and through at least one irrigationfluid port positioned at a tip of the catheter to cool tissue adjacentthe radiofrequency electrode.
 5. The method of claim 2, furthercomprising monitoring electrical activity of the subject using at leastone electrocardiogram electrode, wherein the at least oneelectrocardiogram electrode is positioned along the integrated cathetertip.
 6. The method of claim 2, further comprising operatively couplingthe ablation system to an electrophysiology monitoring system.
 7. Themethod of claim 2, wherein positioning the catheter at a targetanatomical location of the subject comprises manipulating a steerablecatheter or a steerable outer sheath.
 8. The method of claim 2, furthercomprising displaying the determined temperature of tissue on a displayof the ablation system.
 9. The method of claim 2, wherein the operationparameters for the radiometer comprise a slope and an offset describinga temperature response of the radiometer, and wherein the operationparameters for the temperature-measurement device comprise a slope andan offset describing a temperature response of thetemperature-measurement device.
 10. A method of determining atemperature and facilitating ablation of tissue of a subject,comprising: determining a temperature of a tissue of a subject at adepth relative to a surface of the tissue based on, at least in part, asignal generated by a radiometer and a signal generated by atemperature-measurement device, the radiometer and thetemperature-measurement device being positioned at a tip of a catheter;causing energy to be delivered to the tissue of the subject byactivating an ablation member positioned at the tip of the catheter; andautomatically regulating operation of the ablation member based, atleast in part, on the determined temperature.
 11. The method of claim10, wherein automatically regulating the operation of the ablationmember comprises regulating the operation of the ablation member tomaintain the determined temperature of the tissue within a targettemperature setpoint or range.
 12. The method of claim 10, furthercomprising delivering irrigation fluid to a fluid passage of thecatheter and through the at least one irrigation fluid port of thecatheter tip to cool tissue adjacent the ablation member.
 13. The methodof claim 10, further comprising monitoring electrical activity of thesubject using at least one electrocardiogram electrode.
 14. The methodof claim 10, further comprising displaying the determined temperature oftissue on a display.
 15. The method of claim 10, wherein the ablationmember comprises one of a radiofrequency electrode, a microwave energyablation member, a cryoablation member and an ultrasound energy ablationmember.
 16. A method of determining a temperature and facilitatingablation of tissue of a subject, comprising: determining a temperatureof a tissue of a subject at a depth relative to a surface of the tissuebased on, at least in part, a signal generated by a radiometer and asignal generated by a temperature-measurement device configured todetect a temperature along a portion of a catheter; causing energy to bedelivered to the tissue of the subject by activating an ablation memberpositioned along the catheter; and automatically regulating operation ofthe ablation member based, at least in part, on the determinedtemperature.
 17. The method of claim 16, wherein automaticallyregulating the operation of the ablation member comprises regulating theoperation of the ablation member to maintain the determined temperatureof the tissue within a target temperature setpoint or range.
 18. Themethod of claim 16, further comprising delivering irrigation fluid to afluid passage of the catheter and through the at least one irrigationfluid port of the catheter to cool tissue adjacent the ablation member.19. The method of claim 16, further comprising monitoring electricalactivity of the subject using at least one electrocardiogram electrode.20. The method of claim 16, further comprising displaying the determinedtemperature of tissue on a display.
 21. The method of claim 16, whereinthe ablation member comprises one of a radiofrequency electrode, amicrowave energy ablation member, a cryoablation member and anultrasound energy ablation member.